The present invention relates to golf balls, or portions thereof, having fluid-filled centers with a low water activity to inhibit or prevent weight loss through fluid loss, as well as methods of preparing the same.
Conventional golf balls can be divided into several general classes: (a) solid golf balls having one or more layers, and (b) wound golf balls. Two-piece balls are constructed with a generally solid core and a cover and are generally the most popular with recreational golfers because they are very durable and provide maximum distance. Balls having a two-piece construction are commonly formed of a polymeric core encased by a cover. Typically, the core is formed from polybutadiene that is chemically crosslinked with zinc diacrylate and/or other similar crosslinking agents. These balls are generally easy to manufacture, but are regarded as having limited playing characteristics. Solid golf balls also include multi-layer golf balls having a solid core of one or more layers and/or a cover of one or more layers. These balls are regarded as having an extended range of playing characteristics.
Wound golf balls are generally preferred by many players due to their high spin and soft xe2x80x9cfeelxe2x80x9d characteristics. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material and a cover. Wound balls generally are more difficult and expensive to manufacture than solid two-piece balls.
Fluid-filled golf balls, which typically consist of a liquid surrounded by an encapsulating shell further surrounded by a wound layer and one or more cover layers, are often desired for their improved characteristics for short-game shots with irons and putters even though they tend to be more expensive to manufacture and to have a shorter lifespan. Fluid-filled golf balls typically include water to facilitate processing and manufacture, however, water and water-based liquids in golf balls can migrate out of the ball. The encapsulating shell may consist of materials that substantially inhibit the migration of the fluid, but in some cases may not. Various types of fluid-fillings for use in conventional golf balls are discussed in more detail below.
U.S. Pat. No. 5,421,580 discloses a thread-wound golf ball having a liquid-filled center, rubber thread layer formed on the liquid-filled center, and a cover covering the thread layer. The liquid-filled center may be a conventional paste, such as a mixture of water, glycerin, clay, and barium sulfate, and has a diameter of 29.5 mm to 32 mm.
U.S. Pat. No. 5,496,035 discloses a liquid-filled center golf ball having a spherical polymeric shell that contains a liquid mixture of water and a water soluble poly(ethylene oxide) polymer.
U.S. Pat. No. 5,511,791 discloses a thread-wound golf ball having a liquid-filled center containing a paste with a viscosity of 15 to 70 poise at 23xc2x0 C. measured by a type B viscometer. The paste may be prepared by formulating freezing-point depressants, such as glycerine, fillers for adjusting specific gravity, viscosity modifiers, etc., in water.
UK Patent Application No. 2,299,588 A discloses wound golf balls having a center of diameter A of 26 mm to 32 mm and a specific gravity D, where D meets the following relationship: 1.0xe2x89xa6Dxe2x89xa60.9446*A+0.0215*A2-0.00014*A3+14.12. The center may be solid or liquid-filled, but a liquid-filled center is preferred and the liquid may be selected from well-known liquids, for example, water and mixtures of water with barium sulfate, sodium sulfate, or ethylene glycol.
UK Patent Application No. 2,300,125 A discloses a thread-wound golf ball having a liquid-filled center, preferably water, with a specific gravity preferably of 1.0 to 2.0 and a diameter D of 26 mm to 32 mm. The golf ball meets the relationship (A*B)/Dxe2x89xa64.5, where A is the thickness of the rubber bag [shell] containing the liquid and B is the hardness of the bag measured on the JIS-A scale, and the hysteresis loss of the liquid-filled center is up to 7% when the liquid-filled center is deformed to 50% of its diameter D.
U.S. Pat. No. 5,597,365 discloses a thread-wound golf ball having a center of a rubber bag [shell] containing a liquid of, for example, 100 parts by weight water, 5 to 20 parts by weight of a freezing-point depressant, e.g., glycerin, ethylene glycol, etc., 50 to 100 parts by weight of a filler, e.g., barium sulfate, and 10 to 30 parts by weight of a viscosity modifier, e.g., clay. The golf ball is disclosed to have improved characteristics due to the moment of inertia at 23xc2x0 C. is 75 to 80 gcm2 and the rate of increase of the moment of inertia at xe2x88x9230xc2x0 C. compared to that at 23xc2x0 C. is within 2 percent.
U.S. Pat. No. 5,605,512 discloses a thread-wound golf ball having center bag [shell] filled with a liquid. The liquid-filled center is prepared by pouring a liquid into a mold cooled with refrigeration medium, freezing the liquid to make a spherical core, or by pouring a liquid into a crosslinked rubber bag [shell] using a syringe and sealing a mark formed by the injection. This liquid-filled center is frozen and a thread wound in a stretched state around the liquid-filled center, which may be a conventional liquid such as water or paste with barium sulfate, clay, and glycerine dissolved in water. The rubber bag may be made from 10 to 80 weight percent 1,4-cis-polybutadiene and 90 to 20 weight percent natural rubber or cis-isoprene rubber; a metal salt of an unsaturated carboxylic acid; and a peroxide crosslinking agent.
U.S. Pat. No. 5,609,532 discloses a thread-wound golf ball having a solid or liquid-filled center. The liquid-filled center is a bag filled with water or paste obtained by adding barium sulfate and a minor amount of ethylene glycol to water. The center has a diameter of 24 mm to 33 mm, weighs less than 8 grams, and has a specific gravity of less than 0.9.
Publication WO 97/12648 discloses golf balls having a hollow, spherical shell of a polymeric material; a unitary, noncellular core that is a liquid when introduced to the core; and a spherical cover. The liquid may be a gel, such as gelatin, hydrogel, or water/methyl cellulose gel; a hot-melt, such as salt in water or oils or colloidal suspensions; or liquid, such as inorganic salt water solution, hydraulic oils.
U.S. Pat. No. 5,674,137 discloses a thread wound golf ball having a conventional liquid-filled center or solid center. The liquid-filled center liquid preferably is water with a specific gravity of at least 0.9 to 1.5 and may include 4 to 60 weight percent of a fine powder, such as barium sulfate, zinc oxide, or silica and preferably with a mean particle size of 0.02 to 100 xcexcm to adjust the specific gravity to this range. U.S. Pat. No. 5,655,977 discloses a similar thread wound golf ball where the liquid has a specific gravity is 1.08 to 2.00 at 23xc2x0 C. and a viscosity of 1 cPs to 10,000 cPs.
U.S. Pat. No. 5,683,311 discloses a thread wound golf ball having a center bag [shell] filled with a liquid, thread rubber, and a cover. The center bag [shell] preferably has an inner diameter of 24.8 mm to 28.4 mm, a thickness of 1.5 mm to 3.0 mm, and an outer thickness of 29 mm to 33 mm. The bag [shell] is filled with 8 to 12 cm3 of fluid, which can be selected from well-known liquids, such as water; mixtures of water with fine powder, such as barium sulfate, zinc white, and silica; and mixtures of water with sodium sulfate. The water should be at least 50 weight percent of the liquid in the center bag [shell] and have a specific gravity of 1.0 to 2.0.
U.S. Pat. No. 5,683,312 discloses a golf ball having a fluid mass at the center; a first, solid, non-wound mantle layer surrounding the fluid; a second, solid, non-wound mantle layer surrounding the first; and a cover. The fluid may be varied to impart a viscosity and specific gravity as desired to provide desired parameters, such as spin rate, spin decay, compression, and initial velocity. The fluid may be air, water solutions, gels, foams, hot-melts, or even a reactive liquid system that combines to form a solid, and the fluid typically has a viscosity of less than 10 cPs up to 1500 cPs.
Publication WO 98/02213 discloses a golf ball that includes a seamless shell to contain an inert gas above atmospheric pressure, such as nitrogen, helium, and argon. The plastic shell can be a thermosetting resin, thermoplastic material, or an elastomer, but the shell is preferably thermoplastic ionomer.
U.S. Pat. Nos. 5,792,008 and 5,816,938 disclose a wound golf ball having a liquid-filled or paste center in the form of a center bag [shell] filled with a liquid or paste, a thread rubber layer, and a cover. The liquid is water or paste and has a viscosity of 1 cPs to 500 cPs at 20xc2x0 C., and the center has a diameter (D) of 26 to 32 mm. The reference is directed to a formula (A*B/D)xe2x89xa64.5, which should be up to 7% when the center is deformed to 50% of its diameter, where A is gage in mm and B is JIS A hardness of the center bag preferably having a thickness of 1.5 to 3.0 mm. The liquid may include sodium sulfate, aluminum chloride, barium chloride, calcium chloride, copper sulfate, ferrous sulfate, potassium chloride, potassium nitride, or magnesium chloride.
U.S. Pat. No. 5,816,937 discloses a golf ball having a multilayer cover that may include a liquid-filled center, preferably of water, having a specific gravity of 1.0 to 2.3. Additional fillers disclosed for use with the water include barium sulfate, zinc oxide, and silica, as well as a surfactant that may include dodecylbenzenesulfonic acid and sodium dodecylbenzenesulfonate. The rubber bag [shell] may be made of any well-known composition.
U.S. Pat. No. 5,827,133 discloses a golf ball having a reduced spin rate that includes a lubricating layer between the core and the cover. The core is preferably a fluid of either a liquid or gelatinous substance that will not respond to any initial spin imparted to the outer cover and will thereby retard the spin rate of the ball. Suitable liquid materials include several visco-elastic materials, petroleum-based lubricant, or synthetic lubricants, such as mineral oil, polyglycol, and glycerin, and may also include a filler to adjust the specific gravity, such as lead.
U.S. Pat. No. 5,836,831 discloses a brief history of various liquid-filled golf balls, materials for use therein, and processes for making the same. The reference also discloses a variety of thermoplastic materials suitable for use in the envelope or bag [shell] used to contain the liquid in a golf ball.
U.S. Pat. No. 5,846,142 discloses wound golf balls having a wound core and a cover, wherein the core may be solid or a liquid selected from well-known liquids, for example, water and mixtures of water with barium sulfate, sodium sulfate, or ethylene glycol. The liquid is placed in a hollow spherical center bag [shell] made of a conventional rubber composition. The liquid-filled center is disclosed to have a weight in the range of 14 to 23 grams.
As noted above, however, water permeation from the center to the exterior of fluid-filled golf balls is a concern, since a loss of weight tends to occur upon extended storage, especially under low-humidity conditions.
One approach to eliminating or reducing water migration through the ball is the selection of fluid-filled center shell compositions. Different materials vary widely in the rate at which they allow migration and material suppliers frequently supply customers with data regarding the permeation rate and/or the moisture vapor transmission rate (xe2x80x9cMVTRxe2x80x9d) of their polymers. Within a particular family of polymers, for example SURLYN ionomers from E. I. DuPont de Nemours of Wilmington, Del. or PEBAX polyether-amide block copolymers from Elf Atochem of Philadelphia, Pa., the MVTR varies with another material property such as hardness. Though some materials may offer desirable properties, they may be possessed of an undesirably high permeation rate or MVTR. Conversely, materials with low permeation rates or MVTRs may have another undesirable property such as excessive hardness.
It is thus desired to prepare improved fluid-filled golf balls, or portions thereof, having reduced weight loss without a significant accompanying loss in golf ball performance characteristics by means of altering the fluid rather than the accompanying shell.
All of the embodiments according to the invention below may be used in any fluid-filled golf ball.
The invention relates to a golf ball core including a fluid-filled portion having a fluid having a water activity less than about 0.9, and an encapsulating shell including at least one layer which surrounds the fluid-filled portion. In a preferred embodiment, the water activity is less than about 0.8. In a more preferred embodiment, the water activity is less than about 0.6.
In yet another embodiment, the golf ball includes an additional layer disposed about the shell to act as a cover. In a preferred embodiment, the golf ball core includes at least one intermediate layer about the shell and the golf ball further includes a cover layer disposed about the shell. In this embodiment, the at least one intermediate layer may include a tensioned elastomeric material or a solid layer. In one embodiment, the fluid-filled portion includes from about 0.1 cm3 to 20 cm3 of fluid. In a preferred embodiment, the fluid-filled portion includes from about 2 cm3 to 15 cm3 of fluid. In a more preferred embodiment, the fluid-filled portion includes from about 6 cm3 to 10 cm3 of fluid. In yet another embodiment, the shell comprises a thickness from about 5 mils to 500 mils. In another embodiment, the shell is a single layer. In still another embodiment, the shell includes at least one of polyisoprene; natural rubber; a polyether-amide copolymer; a polyether-ester copolymer; or a combination thereof.
In another embodiment, the fluid includes water and a water activity reducing component present in an amount sufficient to inhibit loss of water from the fluid-filled portion. In one embodiment, the water activity reducing component includes at least one of trimethylglycine, 1-carboxy-N,N,N-trimethylmethanaminium hydroxide inner salt, (carboxymethyl)trimethylammonium hydroxide inner salt, glycine betaine, glycocoll trimethylglycine, lycine, oxyneurine, trimethylglycine hydroxide inner salt, trimethylglycocoll anhydride, trimethylglycine hydroxide, 1-carboxy-N,N,N- trimethylmethanaminium chloride, betaine aldehyde chloride, betaine, citrate, betaine ethyl ester chloride, betaine hydrazide hydrochloride, betaine hydrochloride, betaine monohydrate, betaine phosphate, glycerin, sodium aspartate, polydextrose, K2C2H3OH,K2CO3, K2NO3, K2SO4, KBr, KCl, KI, KOH, LiBr, LiCl, LiI, Mg(NO3)2, MgCl2, (NH4)2SO4, NaBr, NaCl, NaI, NaNO3, or ZnBr2. In a preferred embodiment, the water activity reducing component includes at least one of trimethylglycine and sodium chloride.
In another embodiment, the water in the solution is present in an amount from about 30 to 70 weight percent of the total fluid. In another embodiment, the water activity reducing component is present in an amount from about 5 to 90 weight percent of the fluid.
The invention also relates to a method of forming a golf ball core by providing a fluid-filled portion including a fluid that has a water activity less than about 0.9, and containing the fluid in an envelope or shell. In a preferred embodiment, the containing properties of the shell reduces the permeation of the fluid so that less than about 0.4 g of fluid is lost from the fluid-filled center after 120 hours at 110xc2x0 F.
The invention also encompasses a golf ball including a fluid-filled portion having a fluid with a water activity less than about 0.9, a shell including at least one layer that surrounds the fluid-filled portion to inhibit permeation of the fluid through the shell and having an permeation rate of less than about 1,000 (gxc2x7mil)/(100 in2xc2x7day), and a cover disposed about the shell and having a dimple coverage of greater than about 60 percent, a hardness from about 35 to 80 Shore D, and a flexural modulus of greater than about 500 psi, wherein the golf ball has a compression from about 55-120 and a coefficient of restitution of greater than about 0.7.